Farm management weed control

Triazine herbicides provide cost-effective, broad-spectrum weed control and are key tools in conservation tillage. Although the chemical alternatives to the triazines are more costly and generally less efficacious, they are considerably more reliable as weed control methods and more compatible with current farming operations than available nonchemical weed control methods. Even as more com acreage shifts to herbicide-tolerant com, the need remains for residual herbicides such as the triazines to manage resistant weeds and to avoid the need for multiple tillage passes for weed control. 

Fisheries management is primarily concerned with the control of nuisance weeds (33). Herbicides as tools in fish and wildlife management become more important each year. Weed control is reported to be a major phase of fish management in more than a million acres of ponds in southern United States (34). Florida alone has seen the construction in recent years of more than 4000 farm ponds. From 1945-1965, over 1.25 million ponds, plus numerous other water retaining structiures, were built by the Soil Conservation Districts throughout the United States (35). Fishing and other recreational activities in many of these waters, especially those in the southern states, would be impossible without some form of weed control. 

One of the consequences of this approach is that the actual benefits of fertilizers are over estimated in fertility trials relative to when they are used by farmers. In addition, the resulte from adverse years v en no or poor response to fertilizer occurs are usuatty not reported because weather caused no response to the nutrient. Unfortunately, farmers cannot make decisions under a similar lack of constraints they must make investment decisions regarding seed, pesticides, labor, and fertilizer ir uts in a total farm management context. To majd-mize the benefits from management factors, the limiting factors should be in balance with each other, e.g., the crop variety must be able to benefit from the fertilizers used. Weed and insect control, plant density, water availability, tillage, and other management practices should be adequate for the farmer to realize a profit from fertilizer use. 

For example, kochia is normally very sensitive to atrazine and can often be controlled with l.lkg/ha (llb/A) along railroads and on farm lands. However, Burnside et al. (1979) reported that after 13 years of atrazine use, Union Pacific personnel were applying up to 15 kg/ha (13 lb/A) with poor control. These high rates are no longer allowed for atrazine uses. The use of mixtures of triazines and herbicides with alternate modes of action has been an effective management strategy to control weeds resistant to triazines. 

---